Glass feeder made of pt-rh-mo high temperature-high strength alloy

ABSTRACT

This invention pertains to a glass feeder fabricated from an alloy containing 14-79 percent platinum, 20-85 percent rhodium and 0.01-10 percent molybdenum in which said molybdenum is present in an amount sufficient to increase the ductility of the alloy. This invention also pertains to a composite feeder comprising different platinum-rhodium and molybdenum alloys wherein the molybdenum content of these alloys are in an amount sufficient to maintain the resistivities of the alloys at the same magnitude when the feeder is in use at high temperatures.

United States Patent James M. Hansen;

[72] inventors Ralph W. Getz, both of Newark, Ohio [54] GLASS FEEDERMADE OF PT -RH-MO HIGH TEMPERATURE-HIGH STRENGTH ALLOY 4 Claims, NoDrawings [52] U.S.Cl 65/1, 65/374, 75/172 [51 Int. Cl C03b 37/02 [50]Fleld of Search 75/172; 65/1. 374

[56) References Cited UNITED STATES PATENTS 2,460,547 2/ 1 949 Stevens65/374 X Primary ExaminerS. Leon Bashore Assistant Examiner- Robert L.Lindsay, .I r. Allorneys-Staelin and O'verman and Robert E. WittABSTRACT: This invention pertains to a glass feeder fabricated from analloy containing 14-79 percent platinum, 20-85 percent rhodium and0.01-10 percent molybdenum in which said molybdenum is present in anamount sufficient to increase the ductility of the alloy. This inventionalso pertains to a composite feeder comprising differentplatinum-rhodium and molybdenum alloys wherein the molybdenum content ofthese alloys are in an amount sufficient to maintain the resistiviticsof the alloys at the same magnitude when the feeder is in use at hightemperatures.

GLASS FEEDER MADE OF PT-RH-MO HIGH TEMPERATURE-HIGH STRENGTH ALLOYBACKGROUND OF THE INVENTION This invention relates to platinum-rhodiumalloys and more specifically to a platinum-rhodium alloy having a thirdmetal addition wherein its high temperature-high strength properties aregreatly increased. A high rhodium alloy is very desirable because of itshigh melting properties thereby being capable of exposure to highoperating temperatures during service operations.

High rhodium content alloys in the past have been demonstrated to becapable of being produced without difficulty by a normal vacuum meltingprocess. Platinum-rhodium alloys comprising from 20-40 percentrhodium'are capable of being fabricated by a process of hot workingfollowed by normal cold working. For example, in the case of sheetmaterial, hot rolling is followed by cold rolling. Rhodium contents ofmore than 40 percent have been fabricated but they require moresophistication, e. g. powder techniques.

However, by increasing the rhodium content of these alloys theiraffinity for oxygen also increases, i.e. the oxygen solubility of thealloy increases thereby reducing the ductility of the alloy. Extremecare must be taken when using current production welding techniques(tungsten arc-inert gas shield) to prevent brittle welds. The chance ofembrittlement due to oxygen absorption by these alloys is greatestduring welding when the alloy is in the molten state.

During service operation at elevated temperatures. the ductility of ahigh rhodium alloy is reduced by increased oxygen solubility therebycreating a potential for premature failure of the alloy due to stresscracking. Weld failures have been noted on fabricated parts of a highrhodium alloy when exposed to high temperature.

To improve the high temperature ductility of a high rhodium contentalloy and also assure weld integrity, the following high rhodium alloysystem has been developed: platinum 14 to 79 percent, rhodium 20 to 85percent and a third metal addition of from 0.0] to L percent, whereingood homogenization of the third metal addition is required.

The third metal additions are selected from the refractory or platinumgroup metals, such as for example, iridium, tungsten, rhenium andmolybdenum and combinations thereof. Originally selected for use assolid solution strengtheners to yield a stronger alloy, these metalshave been found to increase the high temperature ductility of highrhodium content alloys.

SUMMARY This high temperature-high strength alloy finds immediate use inthe glass fiber industry in bushings and other standard high-temperatureapplications. The development of such an alloy has been prompted by theincreased emphasis on higher melting glasses wherein high strengthrequirements forbushings are necessitated because of the higheroperating temperatures, characteristic of these glasses.

Among the problems encountered when a bushing is in service are thevolatilization losses of the alloy from the bushing and creepdeformation of the bushing structure which decreases the efficiency andlife of the bushing and which leads to lower quality glass fibers.

The advantage of using an alloy of the inventive concept includes areduction in the precious metal volatilization losses from the bushingduring service and improved strength characteristics of the alloy toreduce high temperature creep rates.

Molybdenum is the preferred third metal addition in the platinum-highrhodium content alloys of this invention because of their intended usein high-temperature resistant glass handling apparatus, although theother named third metal additions function in the same manner.Molybdenum is not known in the art to improve the ductility of aplatinumrhodium alloy, so that the use herein of small percentages ofmolybdenum to improve the ductility of a platinum-rhodium alloy istotally unexpected and unobvious. Very small additions of molybdenum toa platinum-rhodium alloy make it possible to use rhodium in proportionsas high as 20 to percent whereas in prior platinum-rhodium alloys,without molybdenum, the maximum practical rhodium content was limited toapproximately 20 to 40 percent.

The percentage of molybdenum that is added to the platinum-rhodium alloyis based upon the rhodium content, i.e. as the latter is increased so isthe former. However, the molybdenum content of the alloy should notexceed 1.0 percent by weight because of the potential of undesirableinternal void formations developing during service applications whichembrittles the alloy.

Some of the general characteristics of the alloy of this inventioninclude improved tensile properties, slightly reduced oxidation lossesof precious metal due to preferential oxidation of the third metaladdition, improved high-temperature ductility, improved creep-rupturelife, and improved weld integrity.

The ranges of proportions of the metals making up the alloys of thisinvention, expressed in weight percent, are:

platinum I 4-79 rhodium 20-85 third metal addition 0.0l l .0

The preferred ranges expressed in weight percent are:

platinum 29-59 rhodium 40-70 third metal addition 0.05-0.75

The preferred composition of the inventive alloy, expressed Alloyscontaining platinum and a high proportion of rhodium typically exhibitvery brittle characteristics unless their purity is very high and theirgas content very low. Even the highest purity alloys however, exhibitsome brittleness especially after exposure to operating temperatures ofl,800 F. to 2,750 F. Due to lattice changes with increasing rhodiumcontent, high-rhodium alloys have a great affinity for gas, particularlyoxygen. The addition of a third element, which forms a volatile oxidemore readily than platinum or rhodium, tends to minimize the effects ofimpurities or dissolved gas on high rhodium content alloys. The effectof the third metal addition of high content rhodium alloys may betheorized by one of the following phenomena: l the third metal elementties up and carries away oxygen thereby preventing formation of a thinfilm of oxide on grain boundaries or (2) the third metal element ties upand carries away oxygen much faster than the diffusion of oxygen in thelattice network, thus preventing embrittlement or (3) the third metalelement tends to further refine and degas the alloy during melting whichresults in improved properties, or (4) the third metal addition acts asan absorbing media for adsorbed and dissolved oxygen in the alloy. It istheorized that the third metal addition is converted to a volatile oxidewhich inhibits oxygen absorption into the alloy. Thus the ductility ofthe alloy is maintained and the high rhodium alloy may be welded andused in high temperature service applications.

It is therefore an object of this invention to provide a platinum-highrhodium content alloy capable of being fabricated into desired articlesand capable of withstanding high operating temperatures.

It is another object to provide an alloy which is highly resistant toattack by molten glass and air, which has good creep'('reep is definedas deformation or elongation as a function of time at a uniform stress,usually at high temperatures.) resistance, good creep-rupture life"(Creep-rupture Life is defined as the time until fracture at a giventemperature and stress), and which has high load carrying ability atelevated temperatures.

These and other objects will be readily apparent from the a homogeneousmix and uniform properties throughout the alloy, and especially to helpdistribute losses of the third metal addition by volatilization.

When a bushing structure is fabricated for use at high serfollowingdetailed description which is intended only to illus- 5 vicetemperatures, it is sometimes desirable to make a comtrate and disclosethe invention. posite structure comprising different alloys having thesame in a platinum-high rhodium content alloy, it is desirable toconstituents but different proportions. For example, the body, have aminimum creep rate. good creep-rupture life and high tip section. andtips of a bushing structure may be fabricated strength at high operatingtemperatures. from platinum-high rhodium content alloys whose composi-Alloys comprising a very high rhodium content (at least 20 tions vary inorder to meet specific operating temperatures. percent) find applicationwhere service temperatures are very More specifically a lower content ofrhodium (20-25percent) high (2,700-2.800 F.) or in high stressapplications at in a platinum-rhodium-X ternary system may be used inthe moderate temperatures (2202.600 F.) to prevent excessive bushingbody to help maintain proper bushing current disdeformation thereof.tribution and to maintain ductility whereas a higher content of It isknown that rhodium is a good hardener for a platinum rhodium (up to 60percent) in a platinum-rhodium-X ternary containing alloy, i.e. it is agood solid solution strengthener system may be used in the tip sectionto reduce the creep and forms a continuous solid solution. Rhodiumsoxidation deformation of the composite structure. resistanceapproximates that of platinum and is therefore the Electricalresistivity plays an important role in the selection basis forselectingaplatinum-rhodium system. of alloys for fabrication intobushings and other apparatus The third metal addition to theplatinum-rhodium y e where electrical current is passed therethrough. Asthe rhodiadds stability to the system in that it extends the operatinglife um content is altered in a platinum-rhodium system to obtain ofarticles fabricated therefrom. The third metal addition specificproperties, the resistivity of the latter is altered. In forms an oxidemore readily than platinum or rhodium and it order for these alloyshaving varying rhodium contents to be volatilizes during weldingoperations thereby maintaining the fabricated into composite bushings,Varying amounts of ductility of the alloy. Without the third metaladdition, the molybdenum are added in Order to Obtain a certainresistivity. ll ld dil b b Oxygen d become b i l d That is, thecomposite structure requires the resistivities thereby be impossible tofabricate and would have a shorter thereof) approximately be of the Samemagnitude- Therefore operating lif the resistivity of these alloys havebeen made to be a function Alloys comprising up to about 40 percentrhodium are comf R molybfienum content f h Importance ofthe merciallyavailable but in order to increase alloy strength, the bemg of the S amemagmwd?S,bFcause,temperamre rhodium content must be increased. However,by increasing dllferenPals would anse as the f thereby the rhodiumcontent, the ductility of the alloy is adversely afdecrefasmg theemcmncy of the fabricated amcle' such as a fected because of the oxygenabsorption, hence the third bushmg' metal addition is employed in theinventive concept to remedy It has been observe? that the ,addmon fsmall of the Situation molybdenum to a platinum-rhodium alloymcreasesthe con- The criteria for the third meta] addition) inc'ude atact angle of the alloy. This charactenstic s critical in the amanufacture of glass fibers to prevent a condition known as Pi of formmga d ox'de P L800 {hm flooding" from occurring. Contact angle is definedas 2 tan vfflauhzes faster than .pkmnum or ,rhodmm a modulus 40 h/xwherein It is the height of a molten bubble of glass on a higher thanthat plaunum or rhodlum Suitable particular substrate and x is theradius of the base of the bubstructure (4) a high valence state(7.8.9,), i.e. its free elec- Flooding is defined as the coveringwetting of a avmlable for bondmg purpose-S to f h strate. such as thetip plate or sidewall of a feeder, housing hols rcs'sufnce and (5) mehmglow projections or tips, with molten glass which disrupts the wllhswnfjSemce temperatures formation of glass fibers. As the contact angleincreases the A desired article or apparatus is usually made from ourtendency toward fl di decreases, thereby di to a platinum-rhodium alloybe forging and rolling it into sheet more f i i operation, form.followed fabrication and However. thC alloy Fgllowing are somecomparative properties for a platinumof this invention is capable ofbeing cast into shapes i.e. slinger h di ll l) versus a l i h di lbcupsvspmnerenesietci denum alloy under various conditions. Theseexamples are A double vacuum melting process is preferred when makingshown by way of illustration and are not intended to be a articles foruse in high temperature applications to help insure limitation of theinventive concepts.

Stress (load applied per Ru ture Percent Creep rate C I 0.02 111. lifeavg.) elongation (1n./in./hr.) omposition (p.s.i. (hrs. (avg.) (avg.)Control -{fifg f 1,000 3m 20. 0 4. 0x10- 1, 000 169. 5 10. 0 5.0X10"Example V weld properties Rh 1 1, 000 276. 9 20. 0 7.3)(10' Control i 1,500 100.0 25. o 1.5x10- Example VI 1, 500 262. 8 12. 0 4.0)(10- ExampleVII 1, 500 421. 9 15. 6 2.8)(10 Stress (load applied per Ru ture PercentCreep rate 0.02 in life avg.) elongation (in./in./hr.) Composition(p.s.i. (hrs (avg.) (avg) Pt 40.00 Example VIII Rh 59.25 1, 500 398. 68. 2.1X10

Mo 0.75 Control g g,?,, 2,000 30.0 25.0 1.0 10-= Example IX 2, 000 58. 938. 0 6.8x 10- Example X 2, 000 45. 7 35. 0 1.2)(10- Example XI 2, 00058. 0 19. 0 2.6)(10 Example XII 2, 000 37. 4 16. 0 2.0x 10- Example XIII2, 000 136. 1 12. 0 9.6X10' Example XIV 2, 000 221. 0 10. 1 0.1 10-Example XV 2, 000 113. 3 12. 5 1 .12X-

Example XVI 2,000 154. 8 5. 6 4.9X10- Control 3, 000 10. 5 47. 0 2.5X10-Example XVI 3, 000 38. 4 20. 0 5.6)(10- Example XVIII 3, 000 51. 5 14. 62.46X10' The measurement of properties of the above examples wasconducted at a temperature of 2,400 F.

A stress was applied to the alloys of each example in order to determinetheir rupture life, percent elongation and creep rate. The control wasan alloy consisting of 75 percent platinum and percent rhodium. When therhodium content was increased and the addition of various amounts ofmolybdenum made thereto, changes in the measured properties wereobserved.

Example I showed a large increase in rupture life, elongation and creeprate when compared to the control whereas example ll showed a slightincrease in rupture life and a slight decrease in elongation and creeprate. What this shows, as well as the other examples is that a greatdegree of flexibility is provided in the various alloys, so that duringfabrication of an apparatus. for example of a bushing used at highservice temperatures, a single alloy or combinations thereof may beselected, depending upon the specific properties desired.

Composite bushing structures were fabricated from theplatinum-rhodium-molybdenum ternary alloy systems of this invention,wherein the compositions for the sidewalls, tip plate, and tips were asfollows, expressed in weight percents:

Platinum Rhodium Molybdenum Sidcwalls 75-85 [5-25 truce Tip plate 60-40-60 up to L0 Tips 70-80 2040 truce sidewall, adapted for containing andcontrollably emitting a plurality of streams of molten glass forformation into glass filaments, fabricated from an alloy consistingessentially of platinum, rhodium and molybdenum, said molybdenum, beingpresent in an amount sufiicient to increase the ductility of the alloy.

2. The feeder as claimed in claim 1 wherein the feeder is fabricatedfrom an alloy comprising, by weight percent, platinum 29 59, rhodium 4070, and molybdenum 0.05 0.75.

3. The feeder as claimed in claim 1 wherein the feeder is fabricatedfrom an alloy comprising, by weight percent, platinum 40.0, rhodium59.5, and molybdenum 0.5.

4. A composite glass feeder having a substantially uniform electricalresistivity, comprising sidewalls, and hollow projections located on aparticular sidewall fabricated from different alloys having the sameconstituents, but in different proportions. consisting of:

l. a high temperature alloy for the sidewalls comprising platinum 75-85percent by weight, rhodium l5-25 percent by weight, and a trace ofmolybdenum; a high temperature alloy for the particular sidewallcomprising platinum 40-60 percent by weight, rhodium 40-60 percent byweight, and up to 1.0 percent by weight of molybdenum, said molybdenumbeing present in an amount sufficient to increase the ductility of thealloy; and 3. a high temperature alloy for the hollow projectionscomprising platinum -80 percent by weight, rhodium 20-30 percent byweight, and a trace of molybdenum; wherein the molybdenum content ofsaid alloys are present in amounts sufficient to maintain theresistivities of the alloys at the same magnitude when the feeder is inuse at high temperatures.

* i *0 I i

2. The feeder as claimed in claim 1 wherein the feeder is fabricatedfrom an alloy comprising, by weight percent, platinum 29 - 59, rhodium40 - 70, and molybdenum 0.05 - 0.75.
 2. a high temperature alloy for theparticular sidewall comprising platinum - 40-60 percent by weight,rhodium - 40-60 percent by weight, and up to 1.0 percent by weight ofmolybdenum, said molybdenum being present in an amount sufficient toincrease the ductility of the alloy; and
 3. a high temperature alloy forthe hollow projections comprising platinum - 70-80 percent by weight,rhodium - 20-30 percent by weight, and a trace of molybdenum; whereinthe molybdenum content of said alloys are present in amounts sufficientto maintain the resistivities of the alloys at the same magnitude whenthe feeder is in use at high temperatures.
 3. The feeder as claimed inclaim 1 wherein the feeder is fabricated from an alloy comprising, byweight percent, platinum 40.0, rhodium 59.5, and molybdenum 0.5.
 4. Acomposite glass feeder having a substantially uniform electricalresistivity, comprising sidewalls, and hollow projections located on aparticular sidewall fabricated from different alloys having the sameconstituents, but in different proportions, consisting of: